1. Field of the Invention
The disclosed system relates to the field of de-icing systems for aircraft structures such as wing and tail surfaces. More specifically, the system relates to the field of using electrothermal heating elements for heating the surface of an aircraft to prevent or remove ice accumulation.
Some de-icing systems may utilize hot gases, known as bleed air, which is bled from engines to critical icing areas such as the leading edges of wings or the nose of the aircraft in the area of the windshield. There are several challenges to the use of bleed air, including, but not limited to, (i) loss of heat during piping of the bleed air to the area of concern, (ii) difficulty of applying direct heat to the area of concern without heating the entire adjacent airframe and internal components, and (iii) the ducting and control system is complex and takes space that could be used for other systems limiting it to larger aircraft.
Other de-icing systems utilize an inflatable boot attached to the external skin of the aircraft. The boots change shape when inflated and break the ice layer, which is then swept away by the airflow over the aircraft. They require maintenance over time and interrupt the airflow over the aircraft even when not in use.
Alternatively some aircraft are provided with systems for dispersing a liquid over the surface of the aircraft to prevent the formation or adherence of ice. The liquids are typically antifreeze solutions such as Glycol that coat the surface and prevent the adherence of ice to the surface. The liquids may be applied through pressurized holes in the leading edge of the wings. The system requires a tank of fluid that must be filled prior to flight, and the liquid creates cleaning issues after application.
An additional type of de-icing system utilizes electric heating to warm the areas of concern sufficient to prevent the formation of ice or to cause ice buildup to shed from the surface of the aircraft. The electricity is generated by the engine or an auxiliary power unit (APU) and the use of electric heating is typically limited by the available power that may be utilized to warm the heaters. As a result electric heating may not be practical for larger areas such as the leading edge of a wing, and may be limited to areas such as duct inlets, for example. The thermal insulation barrier described herein improves the efficiency of electric heating elements thus reducing the load on the engine or APU, and allowing electric heating to be utilized in a wider variety of applications.
2. Description of the Related Art
In many de-icing systems as described above, heating elements are provided adjacent to the skin of the aircraft at points susceptible to icing such as wing and tail surfaces. The heating elements may comprise heater mats that include electrothermal heating devices. The mats may be sandwiched between the skin of the aircraft and the internal structure of the aircraft. The heating elements generate thermal energy that is transferred to the skin of the aircraft for preventing the accumulation of ice.
Some of the thermal energy generated by the heating elements is transferred from the heating elements to the structure of the aircraft instead of to the skin of the aircraft. This thermal energy is transmitted through the internal structure of the aircraft and dissipated without contributing to the prevention of ice accumulation, thus reducing the efficiency and increasing the power requirements of the de-icing system. Various methods of insulating the heating elements from the internal structure of the aircraft have been utilized to reduce the dissipation of thermal energy in the internal structure of the aircraft.
Insulators such as glass beads, epoxy or other similar materials have been disposed between the heating element and the internal structure of the aircraft to reduce heat transfer from the heating element to the internal structure. These materials add weight, expense and complexity to the de-icing system. Such insulating layers also may trap moisture or condensation formed on the insulating layer within the aircraft skin.
The thermal insulation barrier described herein is an improved insulator to support the heating element and reduce thermal losses to the airframe of the aircraft.